AMSTERDAM (Reuters) -- Voters are likely to give the Dutch ruling Christian Democrats a narrow lead over their Labor rivals at national elections in less than three weeks, according to a poll published on Sunday.

Despite the fact that the opposition Labor party leader, Wouter Bos, won a television debate on Friday against Prime Minister Jan Peter Balkenende, the Christian Democrats retained their lead. But the poll showed that the two largest parties will lose some seats to smaller rivals.

Pollster Maurice de Hond put the CDA at 44 seats, down from 45 a week earlier and Labor at 40, down from 42.

But the gap between a CDA-led coalition with its liberal VVD partners and a possible Labor, Socialist Party and Green Left coalition narrowed, as the smaller parties picked up more seats.

Voters said the CDA and the VVD were likely to win a combined 67 seats, just one seat ahead of a projected 66 seats for Labor, the Socialist Party and Green Left. A week earlier, the CDA and VVD had a three-seat lead in the poll.

Labor triumphed in local elections in March, but has seen a commanding opinion poll lead dwindle as the economy has rebounded and Balkenende's CDA has pulled ahead before the Nov. 22 vote.

Balkenende played up the economy's strength in Friday's debate watched by 1.7 million viewers, or about 10 percent of the population, while Bos argued that such growth had come after the center-right government had asked a lot of low and medium income voters but had demanded little of the country's richest.

"With the volatile shifts in the survey from the previous week, a lot can still happen in the coming two and a half weeks," de Hond said in a statement.

Other polls have indicated that the CDA and Labor could win even fewer seats each, which would make a potential grand coalition more likely, like that agreed in Germany last year and now under discussion in Austria.